Ethylene/vinyl acetate / unsaturated esters terpolymer as additives enhancing the low-temperature resistance of liquid hydrocarbons such as middle distillates and motor fuels or other fuels

ABSTRACT

The disclosure relates to the use as an additive improving the resistance to cold and the filterability of motor fuels, of at least one copolymer including:
         78 to 87% in moles of at least one alpha-olefin, preferably at least ethylene,   12 to 18% in moles of at least one vinyl ester, preferably at least vinyl acetate,   1 to 4% in moles of at least one alpha-beta unsaturated mono carboxylic acid ester, preferably at least ethyl-2,hexyl acrylate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Phase Entry of International ApplicationNo. PCT/FR2008/001817, filed on Dec. 23, 2008, which claims priority toFrench Application 07 09 168, filed on Dec. 28, 2007, both of which areincorporated by reference herein.

TECHNICAL FIELD

The invention relates to the use of copolymers of alpha-olefin, vinylester, and alpha, beta-unsaturated carboxylic acid ester as additivesimproving the resistance to cold of motor fuels and lubricants as wellas fuel-oils and the packages containing these copolymers.

BACKGROUND

At a reduced temperature, hydrocarbon compositions, in particular thosewith a medium distillate type base containing paraffin waxes, such asfor example diesel fuels and heating fuel oils exhibit a significantreduction in their rheological properties. It is well known that thecrystallization of paraffins is a factor limiting the use of the middledistillates. It is thus important to prepare diesel fuels which aresuitable for the temperatures at which they are used in motor vehicles,i.e. for the ambient climate. Generally, cold operability of motor fuelsat −10° C. is sufficient in numerous hot or temperate countries.However, in countries with a cold climate, such as the Scandinaviancountries, Canada and the countries of Northern Asia, motor fuel usetemperatures well below −20° C. can be reached. The same is true fordomestic fuel oils stored outside buildings (houses, blocks of flatsetc.). This adequacy of the cold operability of the middle distillatetype motor fuels is important, in particular during cold engine start.If paraffins are crystallized at the bottom of the tank, they may becarried along in the fuel system during starting and block in particularthe filters and pre-filters arranged upstream of the injection systems(pump and injecters). Similarly, for the storage of domestic fuel oils,the paraffins precipitate at the bottom of the tank and can be carriedalong and obstruct the pipes upstream of the pump and the boiler fuelsystem (nozzle and filter). It is evident that the presence of solids,such as paraffin crystals, prevents the normal circulation of the middledistillate.

In order to improve their circulation either in the engine, or towardsthe boilers, several types of additives have appeared. Initially, theoil industry applied itself to the development of cold flow improvers orCFIs promoting the dispersion of the paraffin crystals and thuspreventing them from becoming organized into large networks responsiblefor obstructing the filter pores. These additives essentially act on thecold filter plugging point (CFPP) and the pour point, but do not modifythe cloud point. The prior art has described numerous CFI additives (seefor example U.S. Pat. No. 3,038,479, U.S. Pat. No. 3,627,838, U.S. Pat.No. 3,790,359, U.S. Pat. No. 3,961,961, EP 261957) which are generallycopolymers of ethylene and unsaturated ester, such as ethylene/vinylacetate (EVA), ethylene/vinyl propionate (EVP), ethylene/vinyl ethanoate(EVE), ethylene/methyl methacrylate (EMMA), and ethylene/alkyl fumaratecopolymers. In order to improve the properties of conventional CFIs, theprior art also proposes mixtures of conventional CFI additives ofethylene/unsaturated ester type with lubricants (mono- or polycarboxylicacid and mono- or polyalcohol esters (see for example EP 721492), withanti-sedimentation agents (see for example FR 2490669), or with ethers(see for example U.S. Pat. No. 3,999,960, EP 187488).

Improved CFI additives are also found which are terpolymers orcopolymers deriving from more than 3 separate monomers. For example,U.S. Pat. No. 6,509,424 describes a process for the preparation ofterpolymers of ethylene and at least two compounds containing ethyleneunsaturations, such as vinyl esters, (meth)acrylic esters, vinyl alkylethers in a tubular reactor. These terpolymers can be used as additivesimproving the cold flow of petroleums and petroleum distillates.

U.S. Pat. No. 3,642,459 describes terpolymers comprising 40 to 89% byweight of ethylene, 10 to 40% by weight of vinyl ester derived fromshort-chain carboxylic acid (C2-C4), such as vinyl acetate, andunsaturated monoesters having a C10-C22 alkyl chain); these terpolymersare used as additives to lower the pour point of petroleum distillatesand as anti-wax agents and to improve their filterability. U.S. Pat. No.4,156,434 describes terpolymers of ethylene, vinyl acetate and acrylicester deriving from C12-C24 alcohol which lower the pour point of themotor fuels in which they are incorporated but says nothing about theimprovement of the cold filterability of these additives.

WO 2005/054314 describes useable terpolymers of alpha olefin, vinylester and alpha-beta unsaturated mono carboxylic acid ester. Examplesare given of terpolymers, particularly preferred by the applicant, whichcontain more than 80% in moles of ethylene and less than 9% in moles ofvinyl acetate. Although these terpolymers containing less than 9% inmoles of vinyl acetate have an effect on the reduction of the CFPP formiddle distillates containing more than 18% n-paraffins, they are notsatisfactory as regards solubility on the one hand and blocking tendency(or filterability at ambient temperature) on the other hand: harmfulfilter blocking is noted. EP 1391498 describes additives improving thelow temperature fluidity of middle distillates, namely vinyl polymers(A), preferably ethylene-vinyl ester copolymers, in which the quantityof materials which are insoluble in hexane exceeds 60% by weight at −20°C. and is less than 30% by weight at 10° C.; the examples of EP 1391498clearly show that the filterability temperature (CFPP) is lowered forcopolymers and terpolymers in which the quantity of material which isinsoluble in hexane exceeds 60% by weight at −20° C. and is less than30% by weight at 10° C. in relation to the copolymers and terpolymershaving the same repetition units present in the same proportions but inwhich the quantity of materials which are insoluble in hexane is outsidethe claimed range; the copolymers given as examples are EVA copolymersand ethylene-vinyl acetate-neodecanoate or vinyl 2-ethylhexanoateterpolymers.

There is an unresolved need for additives to improve the resistance tocold of motor fuels (CFPP and pour point) whilst reducing or eveneliminating the risk of blocking, in order to avoid blocking the filtersof the fuel systems of the engines or boilers (injection system andtanks).

SUMMARY

The present invention relates to the use of copolymers as additivesimproving the resistance to cold of motor fuels (CFI additives); thesecopolymers contain units derived from at least one alpha-olefin, atleast one vinyl ester and at least one alpha-beta unsaturated monocarboxylic acid ester, and are preferably terpolymers of ethylene, vinylacetate and ethyl-2,hexyl acrylate. The copolymers according to theinvention which can be used as CFI additives comprise:

78 to 87% in moles of at least one alpha-olefin, preferably at leastethylene,

12 to 18% in moles of at least one vinyl ester, preferably at leastvinyl acetate,

1 to 4% in moles of at least one alpha-beta unsaturated mono carboxylicacid ester, preferably at least ethyl-2, hexyl acrylate.

Advantageously, the copolymers which can be used as CFI additivescomprise:

78 to 87% in moles of ethylene,

12 to 18% in moles of vinyl acetate, preferably 12 to 16% in moles,

1 to 4% in moles of 2, hexyl-ethyl acrylate, preferably 1.5 to 3.5% inmoles.

The copolymers according to the invention which are random copolymershave a numerical molecular weight (Mw) measured by GPC generallycomprised between 3,000 and 30,000, and an average numerical molecularweight (Mn) measured by GPC generally comprised between 1,000 and15,000. These copolymers can be prepared in a known manner by anypolymerization process, (see for example, Ullmann's Encyclopedia ofIndustrial Chemistry, 5^(th) Edition, “Waxes”, Vol. A 28, p. 146; U.S.Pat. No. 3,627,838; EP 7590) in particular by radical polymerization,preferably under high pressure, typically of the order of 1,000 to 3,000bars (100 to 300 MPa), preferably 1,500 to 2,000 bars (150 to 200 MPa),the reaction temperatures generally ranging from 160 to 320° C.,preferably from 200 to 280° C., and in the presence of at least oneradical initiator generally chosen from the organic peroxides and/or theoxygenated or nitrogenated compounds, and a molecular weight regulator(ketone or aliphatic aldehyde etc.). The copolymers can for example beprepared in a tubular reactor according to the process described in U.S.Pat. No. 6,509,424. The hydrocarbon-based compositions in which thecopolymers according to the invention are incorporated are chosen fromall types of fuel oils or motor fuels, such as diesel fuels, domesticfuel oils for heating installations (DF), kerosene, aviation fuels,heavy fuel oils, etc.

Generally the sulphur content of the hydrocarbon compositions is lessthan 5,000 ppm, preferably less than 500 ppm, and more preferably lessthan 50 ppm, or even less than 10 ppm and advantageously sulphur-free.The hydrocarbon-based compositions comprise middle distillates with aboiling temperature comprised between 100 and 500° C.; their initialcrystallization temperature ICT is often greater than or equal to −20°C., generally comprised between −15° C. and +10° C. These distillatescan for example be chosen from distillates obtained by directdistillation of crude hydrocarbons, distillates from vacuumdistillation, hydrotreated distillates, distillates originating fromcatalytic cracking and/or hydrocracking of distillates under vacuum,distillates resulting from conversion processes of ARDS (atmosphericresidue desulphuration) type and/or visbreaking, distillates originatingfrom upgrading of the Fischer-Tropsch cuts, distillates resulting fromBTL (biomass to liquid) conversion of vegetable and/or animal biomass,taken alone or in combination and/or the esters of vegetable and animaloils or their mixtures.

The hydrocarbon compositions can also contain distillates originatingfrom refining operations, which are more complex than those originatingfrom the direct distillation of the hydrocarbons which can for exampleoriginate from cracking, hydrocracking and/or catalytic crackingprocesses and visbreaking processes. They can also contain novel sourcesof distillates, among which there can in particular be mentioned:

-   -   the heaviest cuts originating from the cracking and visbreaking        processes with a high concentration of heavy paraffins,        comprising more than 18 carbon atoms,

synthetic distillates originating from the conversion of gas such asthose originating from the Fischer Tropsch process,

synthetic distillates resulting from the treatment of biomass ofvegetable and/or animal origin, such as in particular NExBTL,

oils and/or esters of vegetable and/or animal oils,

or also biodiesels of animal and/or vegetable origin.

These novel motor fuel bases can be used alone or in a mixture withstandard petroleum middle distillates as a motor fuel base and/ordomestic fuel oil base; they generally comprise long paraffin chainsgreater than or equal to 10 carbon atoms and preferably C14 to C30.

The copolymers as defined previously, with an Mw comprised between 5,000and 27,000 and an Mn comprised between 1,500 and 22,000, preferably withan Mw comprised between 5,000 and 25,000 and an Mn comprised between1,500 and 20,000 are particularly effective when they are incorporatedinto the light middle distillates and/or distillates with a low sulphurcontent (typically less than 50 ppm) and/or at a low initialcrystallization temperature (which may typically be as low as −20° C.).By light middle distillates, is meant distillates in which the contentof n-paraffins having 24 carbon atoms or more ranges from 0 toapproximately less than 0.7% by weight of the total motor fuelcomposition; wherein the C18-C23 n-paraffins represent approximately 3to approximately 5% of the total weight of the motor fuel and whereinthe mass ratio of the C18-C23 n-paraffins to the C24+ paraffinsgenerally ranges from 10 to 35. The copolymers with an Mw comprisedbetween 5,000 and 10,000 and an Mn comprised between 1,500 and 8,000,preferably with an Mw comprised between 5,000 and 8,000 and an Mncomprised between 1,500 and 5,000 are particularly effective when theyare incorporated into heavy middle distillates and/or at a rather highinitial crystallization temperature (typically being able to range from0 to 15° C.). By heavy middle distillates is meant distillates in whichthe content of n-paraffins having 24 carbon atoms or more ranges fromapproximately 0.7 to approximately 2% by weight of the total motor fuelcomposition; wherein the C18-C23 n-paraffins represent approximately 1to approximately 10% of the total weight of the motor fuel and whereinthe mass ratio of the C18-C23 n-paraffins to the C24+ paraffinsgenerally ranges from 1 to 10.

The copolymers can be added to the hydrocarbon compositions as such orpreferably in the form of concentrated solutions, in particularsolutions containing 50 to 80%, preferably 60 to 70% by weight ofcopolymer(s) in a solvent, such as the aliphatic or aromatichydrocarbons, alone or in a mixture (naphtha, kerosene, hydrocarbonfractions such as Solvesso solvent, paraffinic hydrocarbons, such aspentane, hexane.) According to a preferred embodiment of the invention,the hydrocarbon compositions comprise 10 to 5,000 ppm by weight of atleast one copolymer described above optionally, preferably 100 to 1000ppm, and advantageously 150 to 500 ppm.

Apart from the CFI additives or cold resistance additives describedabove, the hydrocarbon compositions can also contain one or more otheradditives different from the copolymers according to the invention,chosen from detergents, anti-corrosive agents, dispersants,demulsifiers, anti-foam agents, biocides, reodorants, procetaneadditives, friction modifiers, lubricity additives or anti-frictionadditives, combustion-promoting agents (catalytic combustion and sootpromoters), cloud point, pour point, cold filter plugging pointimprovers, anti-sedimentation agents, anti-wear agents and/orconductivity modifying agents. Among these additives, there canparticularly be mentioned:

a) procetane additives, in particular (but not limitatively) chosen fromalkyl nitrates, preferably 2-ethyl hexyl nitrate, aroyl peroxides,preferably benzyl peroxide, and alkyl peroxides, preferably ter-butylperoxide;

b) anti-foam additives, in particular (but not limitatively) chosen frompolysiloxanes, oxyalkylated polysiloxanes, and fatty acid amides fromvegetable or animal oils. Examples of such additives are given in EP861182, EP 663000, EP 736590;

c) detergent and/or anti-corrosion additives, in particular (but notlimitatively) chosen from the group constituted by amines, succinimides,alkenylsuccinimides, polyalkylamines, polyalkyl polyamines andpolyetheramines. Examples of such additives are given in EP 938535.

d) lubricity additive or anti-wear agent, in particular (but notlimitatively) chosen from the group constituted by fatty acids and theirester or amide derivatives, in particular glycerol monooleate, and mono-and polycyclic carboxylic acid derivatives. Examples of such additivesare given in the following documents: EP 680506, EP 860494, WO 98/04656,EP 915944, FR 2772783, FR 2772784.

e) cloud point additives, in particular (but not limitatively) chosenfrom the group constituted by long-chain olefin/(meth)acrylicester/maleimide terpolymers, and fumaric/maleic acid ester polymers.Examples of such additives are given in EP 71513, EP 100248, FR 2528051,FR 2528051, FR 2528423, EP 112195, EP 172758, EP 271385, EP 291367;

f) anti-sedimentation additives and/or paraffin dispersants inparticular (but not limitatively) chosen from the group constituted by(meth)acrylic acid/polyamine-amidified alkyl(meth)acrylate copolymers,polyamine alkenylsuccinimides, derivatives of phthalamic acid and ofdouble-chain fatty amine; alkyl phenol resins. Examples of suchadditives are given in EP 261959, EP 593331, EP 674689, EP 327423, EP512889, EP 832172; US 2005/0223631; U.S. Pat. No. 5,998,530; WO93/14178.

g) cold operability multi-functional additives chosen from the groupconstituted by the polymers based on olefin and alkenyl nitrate asdescribed in EP 573 490;

h) other CFI additives improving resistance to cold and filterability,such as EVA and/or EVP copolymers.

These other additives are generally added in a quantity ranging from 100to 1,000 ppm (each). The improved cold-resistance additives according tothe invention can be added to the hydrocarbon compositions within therefinery, and/or be incorporated downstream of the refinery, optionallyin a mixture with other additives, in the form of a package ofadditives.

DETAILED DESCRIPTION Examples

Terpolymers of ethylene, vinyl acetate and ethyl-2,hexyl acrylate weresynthesized in a tubular reactor by radical polymerization under highpressure (1,400 to 2,500 bars (140 to 250 MPa)) and at a polymerizationtemperature of 200 to 280° C. The synthesis was carried out using analiphatic aldehyde (propanal) to control the molecular weights and usingperoxides as polymerization initiators. Table 1 below shows the Mn andMw of the synthesized terpolymers as well as their percentages ofmonomers.

TABLE 1 Characteristics of the polymers synthesized [vinyl [ethyl-2hexyl acetate] acrylate] Copolymer wt. % mol. % wt. % mol. % Mn Mw  128.4 13.1 9.2 2.1  2 550  7 190  2 32.1 15.5 9.7 2.2  2 440  6 870  324.5 11 9.8 2.1  2 480  6 990  4 27 12.1 9 1.9 12 687  14 775   5 28.813.1 9.1 1.9 13 195  15 185   6 (comparative) 13.3 6.6 22.1 5.1 12 627 14 610   7 (comparative) 13.1 6.5 22.4 5.2  8 842 10 460   8(comparative) 17.9 8.9 16.8 3.9 12 875  15 675   9 (comparative) 17.88.8 16.7 3.9  8 384  9 885 10 (comparative) 28.7 14.3 19 4.4 11585 1421011 (comparative) 28.9 14.4 17.5 4.1 12250 14852 12 (comparative) 27.613.7 20.7 4.8 11180 13255 13 (comparative) 28.4 14.1 20.4 4.7 1210014372 14 33.6 16.7 10 2.3  9712 11876 15 31.5 15.7 13.3 3.1 11420 1366716 (comparative) 19.3 9.6 21.5 5  4 498  8 443

The ability to improve the resistance to cold of these terpolymers wasevaluated by incorporating them into 6 engine gas oil type distillatesknown as GOM 1 to GOM 6, the characteristics of which are compiled inTable 2 below.

TABLE 2 Characteristics of the motor fuels GOM 1 GOM 2 GOM 3 GOM 4 GOM 5GOM 6 Distillation ASTM D86 T90-T20 (° C.) 112.7 100.4 96.9 112.2 100.5112 MP-T90 (° C.) 18.6 24.9 26.1 26.2 17 23 T95-° C. 353.9 362.4 351.1350.5 350 356 Cloud point (° C.) −4 −4 −5 −5 −9 −7 NF EN 23015 CFPP (°C.) −5 −7 −6 −5 −9 −6 EN 116 Pour point (° C.) −12 −10 −12 −12 −15 −9 NFT 60105 Paraffins content (% by mass) 19.27 14.68 17.5 18.95 16.1 15.64Chromatography ICT (° C.) −6 −6.3 −6.2 −6.3 −12.6 −9.5 IP 389 Sulphurcontent (ppm) 39.8 38 9 9.5 9.2 48 EN ISO 20846

400 ppm by weight of each copolymer 1 to 16 below was incorporated intothe engine gas oil type distillate called GOM 1, then the FBT (FilterBlocking Tendency) index was measured according to the standard IP 387.The GOM 1 without additives has an FBT index of 1.01.

It is noted that the terpolymers according to the invention make itpossible not to degrade the filter blocking tendency of GOM 1 i.e. thatGOM 1 with 400 ppm of terpolymer added has an FBT of less than 1.41. Theresults are shown in Table 3 below.

TABLE 3 Filter blocking tendency (IP387) of the GOM 1 with 400 ppm ofthe different terpolymers added. Additive added FBT index (IP 387)  11.01  2 1  3 1.3  4 1.14  5 1.06  6 (comparative) 6.08  7 (comparative)6.08  8 (comparative) 1.53  9 (comparative) 1.8 10 (comparative) 1.02 11(comparative) 2.69 12 (comparative) 1.01 13 (comparative) 1.03 14 1.0115 1.01 16 (comparative) 5.1

The cold resistance effectiveness CFPP of the terpolymers incorporatedinto GOM 2 to GOM 6 was measured at a concentration of 140, 210 or 280ppm; the results are compiled in Table 4.

TABLE 4 CFPP effectiveness tests on different gas oils with a lowsulphur content. CFPP (° C.) measurements EN 116 Additive GOM 2 GOM 3GOM 3 GOM 4 GOM 5 GOM 6 added 210 ppm 210 ppm 280 ppm 210 ppm 210 ppm140 ppm 1 −21 −13 −14 −14 2 −16 −15 −14 −14 −16 −14 4 −21 −16 −18 −17 5−19 −15 −15 −12 −10 6 −12 −9 7 −16 −15 −15 −12 −9 8 −12 −9 9 −12 −9 10−12 −13 −13 −13 −10 11 −17 −13 −13 −13 −10 12 −4 −5 −4 −9 13 −5 −4 −3 −914 −12 −11 −5 −17 −10 16 −17 −16 −14 −12 −9

It is noted that the terpolymers 1; 2; 3; 4 according to the inventionare the most effective in the different gas oils GOM 2 to GOM 6.Moreover, from the results in Table 3, it is noted that theseterpolymers 1; 2; 3 and 4 added at a level of 400 ppm to the GOM 1 donot degrade the filter blocking tendency. This is not the case with thecomparative terpolymers 6; 7; 8; 9; 11 and 16 according to WO2005/054314, which greatly degrade the filter blocking tendency measuredaccording to IP 387 and are also not as effective as regards CFPP as theadditives of the invention such as for example the additives 1; 2; 4 and5.

1. A use as an additive improving the resistance to cold andfilterability of motor fuels, of at least one copolymer comprising: 78to 87% in moles of at least one alpha-olefin; 12 to 18% in moles of atleast one vinyl ester; and 1 to 4% in moles of at least one alpha-betaunsaturated mono carboxylic acid ester.
 2. The use according to claim 1of at least one terpolymer comprising: 78 to 87% in moles of ethylene;12 to 18% in moles of vinyl acetate; and 1 to 4% in moles ofethyl-2,hexyl acrylate.
 3. The use according to claim 1 of at least onecopolymer with a numerical molecular weight (Mw) measured by GPCcomprised between 3,000 and 30,000, and an average numerical molecularweight (Mn) measured by GPC generally comprised between 1,000 and20,000.
 4. The use according to claim 1 of at least one copolymer as anadditive improving the resistance to cold and filterability withoutdegrading the filter blocking tendency of middle distillates, such asdiesel fuels, domestic fuel oils for heating installations (DF),kerosene, aviation fuels, and heavy fuel oils.
 5. The use according toclaim 1 of at least one copolymer as an additive improving theresistance to cold and filterability of motor fuels the sulphur contentof which is less than 5,000 ppm, and sulphur-free.
 6. A composition ofhydrocarbons comprising a major quantity of a middle distillate with aboiling temperature ranging from 100 to 500° C. and a minority quantityof at least one copolymer comprising: 78 to 87% in moles of at least onealpha-olefin; 12 to 18% in moles of at least one vinyl ester; and 1 to4% in moles of at least one alpha-beta unsaturated mono carboxylic acidester.
 7. The composition according to claim 6, wherein it contains 0 to100% by weight of biodiesel of at least one of animal and vegetableorigin.
 8. The composition according to claim 6, wherein it is chosenfrom diesel fuels, domestic fuel oils for heating installations (DF),kerosene, aviation fuels, and heavy fuel oils.
 9. The compositionaccording to claim 6, wherein it comprises 10 to 5,000 ppm by weight ofthe at least one copolymer.
 10. The composition according to claim 6,further comprising one or more other additives different from the atleast one copolymer, chosen from at least one of: detergents,anti-corrosive agents, dispersants, demulsifiers, anti foam agents,biocides, reodorants, procetane additives, friction modifiers, lubricityadditives or anti-friction additives, combustion-promoting agents(catalytic combustion and soot promoters), agents improving the cloudpoint, pour point, cold filter plugging point, anti-sedimentationagents, anti-wear agents, and conductivity modifying agents.